Design And Application Of Visible-Infrared Dual-Mode Mechanoluminescence Materials

The material that can emit luminescence under external stress is called mechanoluminescence（ML）material,mainly including visible ML materials and infrared ML materials,with the advantages of direct observation and bright field imaging,respectively.If the advantages of the two can be combined,the problems such as low imaging contract and poor applicability of stress monitoring can be solved,and the application field of ML materials can be widened.Therefore,the development of visible-infrared dual-mode ML materials with high imaging contrast and high stress monitoring applicability has important scientific significance and application value.In this paper,the mechanism of trap regulation and energy transfer has been studied in depth through co-doping two fluorescence ions,and new types of visible and infrared dual-mode ML material have been designed.In addition,the application of dual-mode ML has also been preliminarily explored.The main achievements are as follows:Visible-infrared dual-mode ML material CaZnOS:Bi³⁺,Nd³⁺with high imaging contrast and high saturation threshold has been designed and fabricated.Both Bi³⁺and Nd³⁺replace Ca²⁺sites.The intensity of infrared photoluminescence from Nd³⁺is increased twice by energy transfer from Bi³⁺to Nd³⁺,which proves to be quadrupole-quadrupole interaction.The introduction of Nd³⁺reduces the afterglow of Bi³⁺from2050 s to 122 s,which increases the sign to noise ratio of ML imaging by 5 times.The saturation threshold increases from 620 N to 3000 N,and the thermoluminescence and other multi-spectral analysis reveal that the increase of saturation threshold is related to the decrease of the number of deep traps,which will reduce the utilization efficiency of carriers.Co-doping Nd³⁺can greatly reduce the number of such deep traps.Finally,a smart ML pencil is developed.With this smart pencil,visible ML from Bi³⁺and infrared ML from Nd³⁺can achieve high-contrast handwriting anti-counterfeiting and biological tissue imaging,respectively.Visible-infrared dual-mode ML material CaZnOS:Mn²⁺,Nd³⁺with high applicability in stress monitoring has been designed and fabricated.In the photoluminescent section,the intensity of infrared luminescence from Nd³⁺increases by 8 times due to the energy transfer from Mn²⁺to Nd³⁺.In the ML section,the existence of energy transfer process in ML has been confirmed for the first time.Due to the strong absorption from Nd³⁺,the ML spectrum from Mn²⁺is"split"from one wide peak into two narrow peaks.Through the dynamic analysis of the ML generating,it is found that the efficiency of energy transfer in ML decreases with stress increasing.Based on this,the three more reliable criteria,fluorescence intensity ratio,FWHM and the location of spectrum,for evaluating stress have been proposed.Compared with the traditional method of evaluating by intensity,the accuracy and applicability of stress monitoring are greatly improved,and it is expected to realize the full-scene stress monitoring either in bright field or dark field without external power.